My 3.0 is running hot. I noticed that at normal temperature the top radiator hose is warm but the bottom hose is cold. I'm new to these jaguar but in my experience that tells me the thermostat not working. Just looking for someone with experience with these engines to confirm. Also can someone tell me where the thermostat housing is? I think I know just want to verify before I start disassembling things I don't need to. Thanks.

 

You can read the sordid tale of my thermostat woes here:


https://www.jaguarforums.com/forum/s...rature-186873/


Please note I had a combination of a bad thermostat AND a bad temperature sensor, followed by the replacement thermostat AND sensor being bad from stock. Talk about a troubleshooting nightmare. At the very minimum, I would suggest checking your new and old thermostats in a pot of water on the stove, as shown at the link above. This might save you a LOT of grief.

Replacement procedure for the thermostat is here, courtesy of Gus. You didn't say what year, but this is for the early models. I don't know what differences you may find 2003+:


JagRepair.com - Jaguar Repair Information Resource

 

Thanks for the info. I found the thermostat and replaced it. Just got back from a test drive. The gauge is moving between the middle and half way too hot. Seems like that's where the thermostat opens I guess. Could this be the sensor you mentioned?

 

Whoa, be careful. The temp gauge parks in the middle when the temperature is within a predetermined normal range. From the link I gave earlier:

"More details about the deliberately misleading gauge here:

https://www.jaguarforums.com/forum/x...e-gauge-62813/

That's a different model, but the behavior is the same on my '02."


If your gauge is showing 3/4 of the way to the right, you still have a serious problem. You should never see the gauge that high, unless the car fell into a pit of boiling lava, but in that case make your way to safety and forget about the car. So far, we don't know if you have an actual overheat, an indication issue, or a combination like I had.

Beg, borrow, or steal an infrared thermometer and check the coolant temperature at the thermostat and the radiator inlet. This will help determine exactly what is happening.

Also, what year is your car?

And did you test the new and old thermostats like I suggested? Did the symptoms change with the new thermostat? There's no guarantee the new one is good, so don't fall into that trap.

 

Did you bleed the system?


If air is trapped in the system, it can cause overheat issue, and the fans should definitely come on high.


+1 - need to get a temp gun to check temperatures.

 

Drove the car again today. Had to add coolant beforehand. I'm thinking air found it's way out because the gauge stayed closer to the middle. It sat just a hair to the right of middle and that was after a highway run around 70mph. The new thermostat definitely helped. I am going to find an infrared thermometer and check for sure. By the way I have a 2001 model. It's not my daily driver at the moment so I can take my time and make sure.

 

At that age, I would replace the pressure caps also, cheap, and they do wear out.

Just did both mine, $12 each, and peace of mind, AND, the coolant odour sometimes on the Black car is gone.

 

That's a good idea. I only see one cap. Where is the other one?

 

V12 S Type??????, never mind, its a typo, directly linked to OLD age.

Ya only got one.

 

Trust me I know the feeling. I was thinking about replacing the cap too.

 

What???, a V12 S Type??, or the boring cap replacement??.

We both need a drink.

 

A drink works for me. Although a V12 would get some attention.

 

Okay, I saw your later post with more detail. I thought you were saying the gauge stayed that high continuously. That would be a huge problem.

But now I understand you're saying the gauge briefly went that high and then returned to the center. Depending how (or if) you bled the cooling system, a brief bump on the gauge is normal as air in the cooling system works towards the expansion tank. I'm lazy and have only tried the official bleeding procedure once. Just some normal driving (while watching the temp gauge like a hawk) has been adequate for me. Max heat helps, too. There's even a note buried in the service manual saying driving is okay. The full bleeding procedure is designed for the dealership returning a car to the customer. A customer expects his car back 100% ready to go, instead of listening to gurgling, having erratic heat, and watching the temp gauge act up for the first half hour or so. You also have to top off the reservoir, often several times, so the full bleeding gets around that, too.

Also, be aware how the temp sensor is different on the early V6 models. There is no sensor directly reading coolant temperature, as with nearly all other vehicles. The '99-02 V6 has a Cylinder Head Temperature (CHT) sensor that measures the metal itself, not the coolant. There can be a lag between the metal temperature and the coolant itself.

 

I appreciate the information. I was thinking that the fluctuation on the gauge was related to air bubbles. Every time I drive it the gauge seems be more consistent where it's supposed to be. I'm going to put this in the win column. Thank you all.

 

So, I'm still having temp problems. Since my last response I had to change the radiator. Temp gauge is still wanting to climb. I bought one of those temperature infrared guns and the hottest temperature I got was the upper hose at 182F. That's not even hot enough to open the thermostat yet the fan was on full and the temp gauge was very close to the red. Sounds like a sensor to me, Any other ideas?

 

Why was the radiator changed? Was that a shotgun attempt to fix the overheating?

If 182F is the hottest your new gun is seeing, then the issue certainly sounds like a bad sensor. It's very easy to change on the early V6 models. Search for Jaguar part #XR813484. Aftermarket versions are available, too, if you'd prefer. The sensor is located between the aft two spark plugs on the US driver's side.

 

The radiator was changed due to a crack in the plastic. Not a fun job. Thanks for the part number and general location. That'll help a lot. Still getting used to these new cars.

 

Another update. Got the new sensor in. The temp gauge still starts rising after about 10mins of driving. Could it be something outside the cooling system? The only part I haven't changed in the cooling system is the water pump. Any suggestions?

 

Did you follow the procedure for correctly bleeding the system, including the heater core?

If you haven't already done so, obtain the Workshop Manual and read through the cooling system bleeding procedure.

 

I did not. I'll have to track down one of those manuals. Thanks.